Prop angle of attack vs age

On 2008-07-12, sid wrote:
Looking in my Warrior II Information manual, the prop is listed as a:
Sensenich 74DM6-0-60 or 74DM6-0-58.
Is the "inches of pitch" encoded in that number ?

Yup...the -60 or -58 is the pitch at 3/4 of the blade length. (The 74 is the
diameter in inches.)
--
Jay Maynard, K5ZC http://www.conmicro.com
http://jmaynard.livejournal.com http://www.tronguy.net
Fairmont, MN (FRM) (Yes, that's me!)
AMD Zodiac CH601XLi N55ZC (got it!)

"Maxwell" luv2^fly99@cox.^net wrote in
:


"sid" wrote in message
news:799b2347-57da-401d-b49a-d012f9053f35
@l42g2000hsc.googlegroups.com.
..

Not knowing much about props, what do you mean by "... they are each
2 inches of pitch apart." ?
I thought props were measured in dia. and angle ?

Thanks

--------------------------------------------------------------------

A propellers angle or pitch is expressed in inches. Theoretically, a
24" pitch prop has an angle that would travel 24" forward with each
revolution, at zero angle of attack. The smaller the number, the
flatter the prop.

If that seems confusing, consider a right trangle. If the
circumference of the propeller arc at any given station is the base,
the pitch is the height, and the resulting angle is the pitch angle
for that station. That's why props have less angle at the tip, than at
the root. Theoretically, it keeps the entire lenght of the blade
working at the same angle of attack.

Thus climb props are flatter or less pitch, and cruise props have
more.



nice cuat and paste luser boi.


Bertie

On Fri, 11 Jul 2008 06:00:22 -0700 (PDT), wrote:

On Jul 11, 7:09*am, Stealth Pilot
wrote:
On Fri, 11 Jul 2008 08:57:13 +0000 (UTC), Bertie the Bunyip
wrote:



sid wrote in news:702f8b8d-b77e-452c-904c-
:

On older planes, does the angle of attack change ? Does the prop angle
relax like a motorboat prop does after 1 or 2 decades of constant
use ? (fixed pitch of course)

There are some older warriors on the field (20 - 25) years, and it
seems that there props don't have the bite that the new warrior (10
years old) does.

No, but years of wear and dressing the prop because of nicks and what not
doesn't do them any good at all.

Bertie

I have a fibreglass covered wooden prop which makes it reasonably
resilient in light rain. I paint it.
when the aforesaid light rain has eroded the paint *near the leading
edge I lose 5 knots in cruise speed.

also If I alter the shape with a poor paint coat I lose cruise speed.

the other factor with some commercial aircraft is that there are often
3 props approved for them. a climb, a utility and a cruise prop.
on little cessnas they are each 2 inches of pitch apart.
memories of cruise with a cruise prop would make cruise on a climb
prop seem quite anaemic.

....and what bertie wrote.

Stealth Pilot

I can understand why a poor -- as in not smooth -- paint job would
alter the prop's efficiency, but never would have guessed having a
fractional mm of paint ablated from the leading edge of the prop would
affect it that much. Tongue in cheek question -- did the natural color
of the prop clash with that color and scare the air, or something?

On a serious note, have you any thoughts as to why such a minor change
in shape would have such a remarkable change in efficiency? A 5 knot
change in airspeed is like reducing the manifold an inch or so, isn't
it? That's huge! It also suggests there may be very minor changes in
prop that could improve performance too.

l

the prop had a fairly average sheath put on it. average workmanship.
I use the paint layers to fair the surface to a smoother shape.
the face I see is painted matte black to make it invisible.
the leading edge is blue, the rest varnish.
chipped paint just creates a turbulator which seems to affect this
blade section. (clark Y, aka naca 44xx series)

I got 5 extra knots in cruise for nothing when I cleaned up the prop
and got the shape right the first time. the damaged leading edge paint
just drops me back to the original slower cruise.

Stealth Pilot

On Fri, 11 Jul 2008 09:40:54 -0500, "Maxwell" luv2^fly99@cox.^net
wrote:


wrote in message
...

I can understand why a poor -- as in not smooth -- paint job would
alter the prop's efficiency, but never would have guessed having a
fractional mm of paint ablated from the leading edge of the prop would
affect it that much. Tongue in cheek question -- did the natural color
of the prop clash with that color and scare the air, or something?

On a serious note, have you any thoughts as to why such a minor change
in shape would have such a remarkable change in efficiency? A 5 knot
change in airspeed is like reducing the manifold an inch or so, isn't
it? That's huge! It also suggests there may be very minor changes in
prop that could improve performance too.

---------------------------------------------------

You are absolutely right, and his is just exaggerating again as usual.

Just keep an eye on his posts, you will come to expect it in time.



unlike retards like you maxie I actually regularly fly and have a real
life. I have no need to exaggerate. life is sweet enough for me using
the real numbers.

Stealth Pilot

On Jul 12, 7:39*am, Stealth Pilot
wrote:
On Fri, 11 Jul 2008 09:40:54 -0500, "Maxwell" luv2^fly99@cox.^net
wrote:







wrote in message
....

I can understand why a poor -- as in not smooth -- paint job would
alter the prop's efficiency, but never would have guessed having a
fractional mm of paint ablated from the leading edge of the prop would
affect it that much. Tongue in cheek question -- did the natural color
of the prop clash with that color and scare the air, or something?

On a serious note, have you any thoughts as to why such a minor change
in shape would have such a remarkable change in efficiency? A 5 knot
change in airspeed is like reducing the manifold an inch or so, isn't
it? That's huge! It also suggests there may be very minor changes in
prop that could improve performance too.

---------------------------------------------------

You are absolutely right, and his is just exaggerating again as usual.

Just keep an eye on his posts, you will come to expect it in time.

unlike retards like you maxie I actually regularly fly and have a real
life. I have no need to exaggerate. life is sweet enough for me using
the real numbers.

Stealth Pilot- Hide quoted text -

- Show quoted text -

So of the 2 props, 58" and 60" Which would be considered the cruise
and which is the performance ?
Or are they not far enough apart to tell the difference ?

On Jul 12, 8:37*am, Stealth Pilot
wrote:
On Fri, 11 Jul 2008 06:00:22 -0700 (PDT), wrote:
On Jul 11, 7:09*am, Stealth Pilot
wrote:
On Fri, 11 Jul 2008 08:57:13 +0000 (UTC), Bertie the Bunyip
wrote:

sid wrote in news:702f8b8d-b77e-452c-904c-
:

On older planes, does the angle of attack change ? Does the prop angle
relax like a motorboat prop does after 1 or 2 decades of constant
use ? (fixed pitch of course)

There are some older warriors on the field (20 - 25) years, and it
seems that there props don't have the bite that the new warrior (10
years old) does.

No, but years of wear and dressing the prop because of nicks and what not
doesn't do them any good at all.

Bertie

I have a fibreglass covered wooden prop which makes it reasonably
resilient in light rain. I paint it.
when the aforesaid light rain has eroded the paint *near the leading
edge I lose 5 knots in cruise speed.

also If I alter the shape with a poor paint coat I lose cruise speed.

the other factor with some commercial aircraft is that there are often
3 props approved for them. a climb, a utility and a cruise prop.
on little cessnas they are each 2 inches of pitch apart.
memories of cruise with a cruise prop would make cruise on a climb
prop seem quite anaemic.

....and what bertie wrote.

Stealth Pilot

I can understand why a poor -- as in not smooth -- paint job would
alter the prop's efficiency, but never would have guessed having a
fractional mm of paint ablated from the leading edge of the prop would
affect it that much. Tongue in cheek question -- did the natural color
of the prop clash with that color and scare the air, or something?

On a serious note, have you any thoughts as to why such a minor change
in shape would have such a remarkable change in efficiency? A 5 knot
change in airspeed is like reducing the manifold an inch or so, isn't
it? That's huge! It also suggests there may be very minor changes in
prop that could improve performance too.

l

the prop had a fairly average sheath put on it. average workmanship.
I use the paint layers to fair the surface to a smoother shape.
the face I see is painted matte black to make it invisible.
the leading edge is blue, the rest varnish.
chipped paint just creates a turbulator which seems to affect this
blade section. (clark Y, aka naca 44xx series)

I got 5 extra knots in cruise for nothing when I cleaned up the prop
and got the shape right the first time. the damaged leading edge paint
just drops me back to the original slower cruise.

Stealth Pilot

Five knots is a huge gain. I remember reading some years ago of a
homebuilt getting a new paint job, and the color change on the wings
led to a paint 'bump' or seam near the leading edge which so altered
the airflow the airplane could not fly (probably changed the
stagnation line). Still, that big a change in cruise speed seems
remarkable.

In that I fly behind controllable pitch props it's nothing I'd have
noticed, but still, if TLC gains that kind of speed advantage it
should be standard of care for propellers.

On Sat, 12 Jul 2008 05:49:29 -0700 (PDT), sid
wrote:

On Jul 12, 7:39*am, Stealth Pilot
wrote:
On Fri, 11 Jul 2008 09:40:54 -0500, "Maxwell" luv2^fly99@cox.^net
wrote:







wrote in message
...

I can understand why a poor -- as in not smooth -- paint job would
alter the prop's efficiency, but never would have guessed having a
fractional mm of paint ablated from the leading edge of the prop would
affect it that much. Tongue in cheek question -- did the natural color
of the prop clash with that color and scare the air, or something?

On a serious note, have you any thoughts as to why such a minor change
in shape would have such a remarkable change in efficiency? A 5 knot
change in airspeed is like reducing the manifold an inch or so, isn't
it? That's huge! It also suggests there may be very minor changes in
prop that could improve performance too.

---------------------------------------------------

You are absolutely right, and his is just exaggerating again as usual.

Just keep an eye on his posts, you will come to expect it in time.

unlike retards like you maxie I actually regularly fly and have a real
life. I have no need to exaggerate. life is sweet enough for me using
the real numbers.

Stealth Pilot- Hide quoted text -

- Show quoted text -

So of the 2 props, 58" and 60" Which would be considered the cruise
and which is the performance ?
Or are they not far enough apart to tell the difference ?

the lower the number the finer the pitch.
the cruise prop, ie the one more optimised for higher speed cruise, is
the 60" prop.
the vanilla prop for better climb performance and slower cruise would
be the 58" prop.
you will notice the difference immediately.

if you are thinking of playing with props be careful.

the coarser pitch cruise prop will need more runway for the takeoff
and the climb out will be worse, but once up at altitude and trimmed
for cruise you will see a higher speed.

the lower pitch prop will give better takeoff performance and will
climb you out a little better but will cruise slower.

if you think about it you've just seen the reason variable pitch props
were developed. fine pitch for takeoff and coarse pitch for cruise.

the pitch figure is for the most effective point on the prop which is
the 70% radius position.
here are losses toward the hub and tip losses outboard of that
position so the rule of thumb is to use the 70% position for pitch
calculations.

it isnt hard to work out what your prop is doing. the secret is to get
everything into common units, typically feet per minute.
60" is 5ft. 5ft x 2500rpm = theoretical speed in ft/minute.

cruise speed in knots x 6080 = speed in feet per hour.
divide that by 60 and you have speed in feet per minute.

compare the two and you'll see what the prop's slip is.

if you work out the circumfrence of the circle at the 70% point
and do some arc tan on the pitch vs circumference you can work out the
flying angle of your prop (at the 70% point).

mine flies at close to 4 degrees in cruise.


Stealth Pilot

On Sat, 12 Jul 2008 05:53:59 -0700 (PDT), wrote:

On Jul 12, 8:37*am, Stealth Pilot
wrote:
On Fri, 11 Jul 2008 06:00:22 -0700 (PDT), wrote:
On Jul 11, 7:09*am, Stealth Pilot
wrote:
On Fri, 11 Jul 2008 08:57:13 +0000 (UTC), Bertie the Bunyip
wrote:

sid wrote in news:702f8b8d-b77e-452c-904c-
:

On older planes, does the angle of attack change ? Does the prop angle
relax like a motorboat prop does after 1 or 2 decades of constant
use ? (fixed pitch of course)

There are some older warriors on the field (20 - 25) years, and it
seems that there props don't have the bite that the new warrior (10
years old) does.

No, but years of wear and dressing the prop because of nicks and what not
doesn't do them any good at all.

Bertie

I have a fibreglass covered wooden prop which makes it reasonably
resilient in light rain. I paint it.
when the aforesaid light rain has eroded the paint *near the leading
edge I lose 5 knots in cruise speed.

also If I alter the shape with a poor paint coat I lose cruise speed.

the other factor with some commercial aircraft is that there are often
3 props approved for them. a climb, a utility and a cruise prop.
on little cessnas they are each 2 inches of pitch apart.
memories of cruise with a cruise prop would make cruise on a climb
prop seem quite anaemic.

....and what bertie wrote.

Stealth Pilot

I can understand why a poor -- as in not smooth -- paint job would
alter the prop's efficiency, but never would have guessed having a
fractional mm of paint ablated from the leading edge of the prop would
affect it that much. Tongue in cheek question -- did the natural color
of the prop clash with that color and scare the air, or something?

On a serious note, have you any thoughts as to why such a minor change
in shape would have such a remarkable change in efficiency? A 5 knot
change in airspeed is like reducing the manifold an inch or so, isn't
it? That's huge! It also suggests there may be very minor changes in
prop that could improve performance too.

l

the prop had a fairly average sheath put on it. average workmanship.
I use the paint layers to fair the surface to a smoother shape.
the face I see is painted matte black to make it invisible.
the leading edge is blue, the rest varnish.
chipped paint just creates a turbulator which seems to affect this
blade section. (clark Y, aka naca 44xx series)

I got 5 extra knots in cruise for nothing when I cleaned up the prop
and got the shape right the first time. the damaged leading edge paint
just drops me back to the original slower cruise.

Stealth Pilot

Five knots is a huge gain. I remember reading some years ago of a
homebuilt getting a new paint job, and the color change on the wings
led to a paint 'bump' or seam near the leading edge which so altered
the airflow the airplane could not fly (probably changed the
stagnation line). Still, that big a change in cruise speed seems
remarkable.

In that I fly behind controllable pitch props it's nothing I'd have
noticed, but still, if TLC gains that kind of speed advantage it
should be standard of care for propellers.

I repainted the prop (and rebalanced it) and replaced the windscreen
plastic and saw an 11knot increase in cruise speed.
this is after an extensive period of taping up seams and other toying
that saw absolutely no improvement at all.

it took my aero engineer friend about a month to work out what I'd
accidently done.

it was ...put back all the windscreen bolts.

this removed some blasts of air into the low pressure zone over the
windscreen.
the blasts of air were doing two things my aero engineer friend
deduced.
reducing the depression in pressure over the wing which reduced the
lift and required a slight increase in angle of attack which increased
induced drag.
increased the thickness of the boundary layer which increased drag.

the jump in performance on the first flight was just stunning to
behold. where before I could just make 120 knots balls to the wall in
a flypast I can now easily achieve 145 knots at max rpm after a dive.

your controllable prop gives you so much of an advantage.

Stealth Pilot

On Jul 13, 12:53*am, wrote:
On Jul 12, 8:37*am, Stealth Pilot
wrote:



On Fri, 11 Jul 2008 06:00:22 -0700 (PDT), wrote:
On Jul 11, 7:09*am, Stealth Pilot
wrote:
On Fri, 11 Jul 2008 08:57:13 +0000 (UTC), Bertie the Bunyip
wrote:

sid wrote in news:702f8b8d-b77e-452c-904c-
:

On older planes, does the angle of attack change ? Does the prop angle
relax like a motorboat prop does after 1 or 2 decades of constant
use ? (fixed pitch of course)

There are some older warriors on the field (20 - 25) years, and it
seems that there props don't have the bite that the new warrior (10
years old) does.

No, but years of wear and dressing the prop because of nicks and what not
doesn't do them any good at all.

Bertie

I have a fibreglass covered wooden prop which makes it reasonably
resilient in light rain. I paint it.
when the aforesaid light rain has eroded the paint *near the leading
edge I lose 5 knots in cruise speed.

also If I alter the shape with a poor paint coat I lose cruise speed..

the other factor with some commercial aircraft is that there are often
3 props approved for them. a climb, a utility and a cruise prop.
on little cessnas they are each 2 inches of pitch apart.
memories of cruise with a cruise prop would make cruise on a climb
prop seem quite anaemic.

....and what bertie wrote.

Stealth Pilot

I can understand why a poor -- as in not smooth -- paint job would
alter the prop's efficiency, but never would have guessed having a
fractional mm of paint ablated from the leading edge of the prop would
affect it that much. Tongue in cheek question -- did the natural color
of the prop clash with that color and scare the air, or something?

On a serious note, have you any thoughts as to why such a minor change
in shape would have such a remarkable change in efficiency? A 5 knot
change in airspeed is like reducing the manifold an inch or so, isn't
it? That's huge! It also suggests there may be very minor changes in
prop that could improve performance too.

l

the prop had a fairly average sheath put on it. average workmanship.
I use the paint layers to fair the surface to a smoother shape.
the face I see is painted matte black to make it invisible.
the leading edge is blue, the rest varnish.
chipped paint just creates a turbulator which seems to affect this
blade section. (clark Y, aka naca 44xx series)

I got 5 extra knots in cruise for nothing when I cleaned up the prop
and got the shape right the first time. the damaged leading edge paint
just drops me back to the original slower cruise.

Stealth Pilot

Five knots is a huge gain. I remember reading some years ago of a
homebuilt getting a new paint job, and the color change on the wings
led to a paint 'bump' or seam near the leading edge which so altered
the airflow the airplane could not fly (probably changed the
stagnation line).

Sounds like a myth to me. How thick is a paint line?

Still, that big a change in cruise speed seems
remarkable.

I'd say unlikely.

Cheers

"Maxwell" luv2^fly99@cox.^net wrote in news:dt4ek.20332$%q.3231
@newsfe24.lga:


"More_Flaps" wrote in message
...

I'd say unlikely.

Cheers


Or hallucination.



Your an hullucination?


I thought you were more sort of a bad dream. the kind you have whne you eat
too many chilli dogs.


Bertie